Veins have a vital role of working with the arteires and capillaries, so lets explain what they do.

Our veins are a key part of the cardiovascular system, transporting waste-rich blood back to the lungs and heart

How are veins constructed.

Like arteries, veins have three layers: an outer layer of tissue, a middle layer of muscle, and a smooth inner layer of epithelial cells to allow the blood to move easily. Where they differ from arteries is that the layers are thinner they transport blood at a lower pressure, and are thus not as strong.

Role of veins.

Because veins receive blood from the capillaries after the exchange of oxygen and carbon dioxide has taken place, the blood they move is waste-rich it must be transported back to the lungs and heart in order to dispose of this waste and start the process again.

Clearly it is important that these waste products cant flow backwards. We thus have a series of valves, located inside the vessels. These valves serve two functions. Firstly, they keep waste-rich blood flowing toward the heart. Secondly, they allow the whole system to work, even against gravity the blood that is moving up the leg from the foot towards the heart has a series of footholds to help it climb its way back up.

Understanding why blood looks blue in the veins.

The blood that flows through these vessels and back to the heart is a deep colour, almost maroon. When seen through your skin, for example in your wrists, or hands, or ankles, it can actually appear to be blue, as the skin refracts light.

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